Since automobiles in general travel at considerably high speed, every driver needs to direct his effort at driving the car without having his attention diverted otherwise. When a driver wants to know such instant information values as speed, time, rpm, fuel level, temperature, humidity, etc., hazardous accidents may result if he has his eyesight off the course. Therefore, various head-up display designs have been introduced. In know head-up displays for automobiles, some will exhibit the so-called double images which produce the image deviation due to the projection on the thick transparent glass facing, others will result in distortion of the displayed images due to the inclined reflective surface (when the principle of reflection is used), still others will cause shift in the image (direct projection) due to the relative motion when an automobile is accelerating (according to the Doppler effect), thus leading to blindness.